Tuberculosis treatment failure and drug resistance--same strain or reinfection?

Effects of isoniazid resistance on TB treatment outcomes under programmatic conditions in a high-TB and -HIV setting: a prospective multicentre study

Objectives

The scale and impact of background isoniazid resistance in TB- and HIV-endemic countries requires definition to improve treatment success and guide the scale-up of isoniazid preventive therapy (IPT). We describe the effects of isoniazid resistance on TB treatment outcomes among patients with or without HIV infection in Dar es Salaam, Tanzania.

Methods

A multicentre, prospective observational study was conducted among TB patients commencing WHO-recommended first-line TB treatment. In multivariate analysis we ascertained the relationship between isoniazid resistance at presentation with a composite of poor treatment outcomes (death, failure or default from TB therapy).

Results

Of 861 patients, 250 (29.0%) were HIV infected and 23 (2.7%) had isoniazid resistance. Seven hundred and ninety-seven (92.6%) of the patients were successfully treated and 25 (2.9%) died. Isoniazid resistance [relative risk (RR) = 6.0; 95% CI = 1.9-18.7; P  <   0.01] and HIV infection with (RR = 2.3; 95% CI = 1.0-5.2; P  =   0.05) or without (RR = 3.1; 95% CI = 1.5-6.2; P  <   0.01) ART were independent predictors of poor treatment outcomes.

Conclusions

Background isoniazid resistance and HIV infection adversely affected TB treatment outcomes. Early laboratory detection of isoniazid resistance is important for successful TB therapy. Studies on the impact of background isoniazid resistance on the efficacy of isoniazid prophylaxis are recommended.

Rifapentine-loaded PLGA microparticles for tuberculosis inhaled therapy: Preparation and in vitro aerosol characterization

Inhaled delivery of drugs incorporated into poly (lactic-co-glycolic acid) (PLGA) microparticles allows a sustained lung concentration and encourages phagocytosis by alveolar macrophages that harboring Mycobacterium tuberculosis. However, limited data are available on the effects of physicochemical properties of PLGA, including the monomer ratio (lactide:glycide) and molecular weight (MW) on the aerosol performance, macrophage uptake, and toxicity profile. The present study aims to address this knowledge gap, using PLGAs with monomer ratios of 50:50, 75:25 and 85:15, MW ranged 24 - 240kDa and an anti-tuberculosis (TB) drug, rifapentine. The PLGA-rifapentine powders were produced through a solution spray drying technique. The particles were spherical with a smooth surface and a volume median diameter around 2μm (span ~2). When the powders were dispersed using an Osmohaler(®) at 100L/min for 2.4s, the fine particle fraction (FPFtotal, wt.% particles in aerosol <5μm relative to the total recovered drug mass) was ranged between 52 and 57%, with no significant difference between the formulations. This result suggests that the monomer ratio and MW are not crucial parameters for the aerosol performance of PLGA. The phagocytosis analysis was performed using Thp-1 monocyte-derived macrophages. The highest rate of uptake was observed in PLGA 85:15 followed by 75:25 and 50:50 with about 90%, 80% and 70%, respectively phagocytosis over 4h of exposure. Furthermore, the cytotoxicity analysis on Thp-1 and human lung adenocarcinoma epithelial cells demonstrated that PLGA concentration up to 1.5mg/mL, regardless of the monomer composition and MW, were non-toxic. In conclusion, the monomer ratio and MW are not crucial in determining the aerosol performance and cytotoxicity profile of PLGA however, the particles with high lactide composition have a superior tendency for macrophage uptake.

Antituberculosis drug resistance acquired during treatment: an analysis of cases reported in California, 1994-2006

BACKGROUND

To inform efforts to prevent antituberculosis drug resistance acquired during treatment, particularly multidrug-resistant (MDR) tuberculosis, we analyzed surveillance records from the US state with the highest morbidity.

METHODS

Surveillance data from the California tuberculosis registry of cases reported between 1994 and 2006 were examined retrospectively. Crude risks of acquired resistance were estimated. Multivariate logistic regression was used to estimate odds ratios of demographic, clinical, and case management characteristics associated with acquired drug resistance (ADR), and secular trends in the incidence of ADR were assessed.

RESULTS

One in 688 patients acquired MDR tuberculosis, with crude risks varying greatly by initial drug susceptibility test results: 1 in 1909 if initially susceptible to isoniazid and rifampin, 1 in 113 if initially isoniazid resistant, and 1 in 23 if initially rifampicin resistant. Acquired isoniazid and rifampicin monoresistance occurred in 1 in 1018 and 1 in 1455 patients, respectively. Independent predictors of acquired MDR tuberculosis were initial isoniazid resistance (odds ratio [OR], 19.2; 95% confidence interval [CI], 8.25-44.7; P < .001), initial rifampicin resistance (OR, 35.9; 95% CI, 8.61-150; P < .001), human immunodeficiency virus (HIV) infection (OR, 5.07; 95% CI, 1.73-14.9; P = .003), and cavitary disease in the absence of directly observed therapy throughout therapy (OR, 2.65; 95% CI, 1.05-6.69; P = .04). The annual incidence of ADR declined over the study period.

CONCLUSIONS

Although ADR is rare and declining in California, its costly consequences warrant improvements in treatment practices. Our findings suggest that we ensure DOT throughout the course of therapy for patients with baseline drug resistance, cavitary disease, or HIV infection.

Modeling the dynamic relationship between HIV and the risk of drug-resistant tuberculosis

The emergence of highly drug-resistant tuberculosis (TB) and interactions between TB and HIV epidemics pose serious challenges for TB control. Previous researchers have presented several hypotheses for why HIV-coinfected TB patients may suffer an increased risk of drug-resistant TB (DRTB) compared to other TB patients. Although some studies have found a positive association between an individual's HIV status and his or her subsequent risk of multidrug-resistant TB (MDRTB), the observed individual-level relationship between HIV and DRTB varies substantially among settings. Here, we develop a modeling framework to explore the effect of HIV on the dynamics of DRTB. The model captures the acquisition of resistance to important classes of TB drugs, imposes fitness costs associated with resistance-conferring mutations, and allows for subsequent restoration of fitness because of compensatory mutations. Despite uncertainty in several key parameters, we demonstrate epidemic behavior that is robust over a range of assumptions. Whereas HIV facilitates the emergence of MDRTB within a community over several decades, HIV-seropositive individuals presenting with TB may, counterintuitively, be at lower risk of drug-resistant TB at early stages of the co-epidemic. This situation arises because many individuals with incident HIV infection will already harbor latent Mycobacterium tuberculosis infection acquired at an earlier time when drug resistance was less prevalent. We find that the rise of HIV can increase the prevalence of MDRTB within populations even as it lowers the average fitness of circulating MDRTB strains compared to similar populations unaffected by HIV. Preferential social mixing among individuals with similar HIV status and lower average CD4 counts among HIV-seropositive individuals further increase the expected burden of MDRTB. This model suggests that the individual-level association between HIV and drug-resistant forms of TB is dynamic, and therefore, cross-sectional studies that do not report a positive individual-level association will not provide assurance that HIV does not exacerbate the burden of resistant TB in the community.

Treatment outcomes and relapses of pulmonary tuberculosis in Lazio, Italy, 1999-2001: a six-year follow-up study

OBJECTIVES

The aim of this study was to enhance tuberculosis (TB) treatment outcome monitoring by linking diverse surveillance systems and estimating treatment outcomes including relapse.

METHODS

Tuberculosis treatment was surveyed in the Lazio region (Italy) from 1999 to 2001; a six-year follow-up of notified cases was undertaken to detect relapses. The results were analyzed as a population-based case-control study comparing each unsuccessful outcome and relapse with eligible controls.

RESULTS

Of the 974 patients who entered the survey, 805 (82.6%) had complete treatment evaluations; 398 (49.4%) had a successful outcome, 401 (49.8%) had an unsuccessful outcome, and six developed chronic TB. Death was associated with age >64 years (OR 5.9; 95% CI 3.1-11.2), male gender (OR 2.1; 95% CI 1.0-4.4), and using second-line drugs (OR 2.3; 95% CI 1.0-5.4). Treatment failure was associated with previous treatment (OR 3.0; 95% CI 1.4-6.7) and being male, being foreign born (OR 6.6; 95% CI 2.1-21.2), receiving second-line drugs (OR 7.4; 95% CI 1.8-29.5), and receiving modified therapy (OR 5.1; 95% CI 1.7-14.9). Relapses after successful outcomes were detected in 5.5%, for which the strongest predictor was having extrapulmonary lesions (OR 22.8; 95% CI 1.8-287.3).

CONCLUSIONS

Linking our survey data to other surveillance systems improved the mortality estimates and detected a high rate of relapse. Having received previous treatment and being a foreigner were independent determinants of treatment failure, suggesting that both acquired and primary drug resistance affect TB patients in Lazio.

Mixed infection and clonal representativeness of a single sputum sample in tuberculosis patients from a penitentiary hospital in Georgia

Background

Studies on recurrent tuberculosis (TB), TB molecular epidemiology and drug susceptibility testing rely on the analysis of one Mycobacterium tuberculosis isolate from a single sputum sample collected at different disease episodes. This scheme rests on the postulate that a culture of one sputum sample is homogeneous and representative of the total bacillary population in a patient.

Methods

We systematically analysed several pre-treatment isolates from each of 199 smear-positive male adult inmates admitted to a prison TB hospital by standard IS6110 DNA fingerprinting, followed by PCR typing based on multiple loci containing variable number of tandem repeats (VNTRs) on a subset of isolates. Drug susceptibility testing (DST) was performed on all isolates for isoniazid, rifampicin, streptomycin and ethambutol.

Results

We found mixed infection in 26 (13.1%) cases. In contrast, analysis of a single pre-treatment isolate per patient would have led to missed mixed infections in all or 14 of these 26 cases by using only standard DNA fingerprinting or the PCR multilocus-based method, respectively. Differences in DST among isolates from the same patient were observed in 10 cases, of which 6 were from patients with mixed infection.

Conclusion

These results suggest that the actual heterogeneity of the bacillary population in patients, especially in high TB incidence settings, may be frequently underestimated using current analytical schemes. These findings have therefore important implications for correct interpretation and evaluation of molecular epidemiology data and in treatment evaluations.

Molecular Epidemiology: A Tool for Understanding Control of Tuberculosis Transmission

One of the primary goals of tuberculosis control programs is to interrupt the transmission of Mycobacterium tuberculosis. The development of several genotyping tools has allowed tracking of strains of M. tuberculosis as they spread through communities. Studies that have combined the use of genotyping with conventional epidemiologic investigation have increased the understanding of the transmission and pathogenesis of tuberculosis. This article reviews some of the lessons learned using these new epidemiologic tools.

Incidence and Drug Susceptibility pattern of Mycobacterium tuberculosis in HIV infected Patien

Incidence of HIV infection in patients with tuberculosis was found out by serological method (ELISA) with confirmation by Western Blot analysis. Out of 2116 tuberculosis patients tested for HIV, 150 cases were found to be positive for HIV infection (5.73%). Drug susceptibility to first line antitubercular drugs was carried out in 1378 isolates from HIV negative cases and 68 isolates from AIDS cases. The overall resistance pattern to one or more drugs was seen in 13.78% of isolates from HIV negative cases as compared to 7.2% isolates in AIDS cases. Multidrug resistance (MDR) was seen in 8.9% of isolates from HIV negative cases as compared to 4.4% of isolates from AIDS cases.

Molecular differentiation of Mycobacterium bovis isolates. Review of main techniques and applications

Until recently, none of the Mycobacterium bovis typing techniques permitted a satisfactory differentiation of isolates. During the last 10 years, the genome of pathogenic mycobacteria has been extensively studied, and phylogenetic analyses have shown that all (except Mycobacterium avium) belong to a single genetic species: the Mycobacterium tuberculosis complex. This increase in knowledge about the genome of these bacteria has lead to the discovery of molecular markers that allow us to differentiate isolates. Because of the phylogenetic proximity of the strains, even if most of these markers have been discovered in M. tuberculosis, they could be successfully adapted to the other bacteria of the M. tuberculosis complex, especially M. bovis. The most common markers in use today are the IS6110 insertion sequence, the direct repeat (DR) region, the poly(GC) rich (PGRS) sequences and the variable number tandem repeats (VNTR) sequences. The corresponding typing techniques are briefly described, and current knowledge of polymorphism and marker stability is detailed. If molecular markers are to offer wide perspectives for field studies, these two characteristics (polymorphism and stability) must be taken into account when choosing the marker(s) used in a study. In this context, examples of the application of molecular typing techniques for M. bovis are reviewed, on the one hand with epidemiological studies for which the major problem is the comparison between isolates and, on the other, with more general studies about the population genetics of M. bovis in a given country, and about its history and its phylogeny.